The present invention relates to a connecting device of a soil removing member for an excavator, which is used in a construction for laying a pipe member underground.
In an underground construction under a road or river for laying a pipe member, for example a water pipe or gas pipe, a departure or starting pit and an arrival pit are dug at both sides of the construction, and in the departure pit, a digging apparatus such as a ground boring machine is disposed to install the pipe member while digging and moving toward the arrival pit. Accordingly, excavated soil and sand at a front part of the pipe are sent out rearwardly by an auger screw provided inside the pipe member.
In this pipe-inserting or installing work, while the pipe member is advanced and extended under the ground, the auger screw is extended by a predetermined connecting member.
Conventionally, as the connecting member for the auger screw, for example, structures as shown in FIGS. 9(a)-9(d) are known. In the case shown in FIG. 9(a), a male screw 51 projected at one end of one rotational shaft 50 engages a female screw 52 bored in the other end of another rotational shaft 50 to connect the same.
Also, in the case shown in FIG. 9(b), one end and the other end of the rotational shaft 50' are provided with rectangular pipe like attaching portions 53, 54, and a retractable knock 55 is attached on an outer periphery of the attaching portion 53. After the attaching portions 53, 54 are fitted, the knock 55 is engaged with a receiving hole 56 in the other attaching portion 54 to connect the attaching portions 53, 54.
In the case shown in FIG. 9(c), one end and the other end of the rotational shaft 50a are provided with rectangular pipe like attaching portions 53a, 54a, wherein after both attaching portions 53a, 54a are fitted, parts of through holes 57, 57' in the attaching portions 53a, 54a are firmly tightened by a bolt 58 and a nut 59 to connect the attaching portions 53', 54'.
Further, in the case shown in FIG. 9(d), one end and the other end of rotational shaft 50b are provided with splined attaching portions 53b, 54b, wherein after both attaching portions 53b, 54b are fitted, the attaching portions 53b, 54b are surrounded and held by a connection band 60, which is tightened by a bolt and a nut to connect the attaching portions 53b, 54b.
However, although the connection operations can be easily carried out in these structures, these structures have various problems as follows. In the screw-in type shown in FIG. 9(a), in case the screw does not rotate because sand and soil are stuck in the auger, the screw is reversely rotated to be pulled out, and then inserted again; in this case, by this reverse rotation, the connection at the screw part might be disengaged. On the other hand, after installing the pipe, when the screw is disassembled, loosening of the screw is difficult due to the strong engagement in the positive direction, so that workability of disassembling of the pipe is greatly lowered.
Also, in the fit-in knock type shown in FIG. 9(b), since the strong tensile strength is concentrated on the knock itself, there is a disadvantage that this knock portion tends to break down. Additionally, since a leaf spring for retractably urging the knock is mounted inside the rectangular pipe member, due to storing space therefor, the rectangular pipe has to be formed thin, so that the strength thereof is lowered.
In the fit-in bolt tightening type shown in FIG. 9(c), the bolt is very weak against the torque load, thrust load and distortion force; and especially, damages at the screw of the bolt and the nut portion, or bend of the bolt are frequently happened. Accordingly, there are cases such that the screw portions can not be unscrewed in disassembly, and the bolt and the nut are unscrewed while the device is in use.
Furthermore, in the inserting-band tightening type shown in FIG. 9(d), since the clamping portion of the bolt in the band is protruded outwardly, rocks or the like taken into the inserted pipe hit this clamping portion to cause rotational resistance, so that a large torque for propelling or advancing the machine is necessary, resulting in causing troubles for transferring the removed soils rearwardly. Also, members such as the band, bolt and nut, and tightening tools are necessary, so that connection workability is extremely poor, and workability of detaching and attaching the shafts is drastically lowered.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a connecting device of a soil removing member for an excavator, wherein the work for detaching and attaching the soil removing members with each other can be easily and securely carried out by one-touch operation, and moreover, the outer periphery of the connecting device does not include a projection so that smooth removal of soil can be achieved.
Further objects and advantages of the invention will be apparent from the following description of the invention.